Cobalt alloy



United States Patent 3,362,816 COBALT ALLOY Heinrich Winter, Eschborn,Taunus, and Horst Kiupel,

Langen, Germany, assiguors to the Federal Republic of Germany asrepresented by the Secretary of Defense, Bonn, Germany N0 Drawing. FiledJune 19, 1964, Ser. No. 376,582 Claims priority, application Germany,June 22, 1963,

2 Claims. (Cl. 75-171) Percent by weight Cobalt 55 Chromium 20 Tungsten15 Nickel Our investigations concerning the incorporation of a hardtemperature stable finely dispersed phase into an alloy of said type asmatrix had the surprising result that a considerable improvement of thehigh temperature strength is attained when zirconium and boron, in anatomic proportion of about 1:2, corresponding to the compound ZrB areadded to the melt in a total amount of up to about 12, preferably 1.5 to3 percent by Weight of the alloy.

Already 0.5% by weight of such a Zr+2B addition to the base alloyproduces a considerable increase of the high temperature properties. At800 C. the hardness HV 5 increased from 98 to 134 kg./Inm. (The HVvalues designate the Vickers hardness, the numbers 5 etc, referring tothe load in kg. applied for the test, in accordance with the ofiicialGerman testing standards, published as DIN 50133.)

Percent by Weight Cobalt 55 Chromium 20 Tungsten Nickel 5 Molybdenum 5In such alloys, the malleability even increases up to an addition of 2%ZrB while also the strength characteristics at high temperatures show astrong increase. Above said limit, the malleability decreases again buteven with an addition of 12% ZrB the alloy is not yet completelyembrittled.

An alloy of the character described, containing 5% Mo and 1.5% ZrBtested in the cast state, had at room temperature an HV 30 of 357 kg/mm.and at 800 C. an HV 5 of 262 kg./mm.

It is surprising that forming the alloy and subsequent annealing forseveral hours at temperatures up to and exceeding 900 C. does notproduce a decrease of the strength properties at room temperature but afurther increase. The following values were measured at an alloycontaining 5% Mo and 1.5% ZrB reduced by 50%.

HV 30 at room temperature 550 HV 5 at 800 C. 374 HV 30 after 3 hoursannealing at 900 C. at room temperature 625 At the same time, thestrength properties up to temperatures exceeding 1000 C. Wereconsiderably increased. Particularly at temperatures about 900 C., thenovel alloys have better high temperature characteristics than thehardenable nickel base superalloys. In said alloys, the phases producingthe hardening in the nickel-solid solution, such as Ni Al or Ni Ti,dissolve at temperatures slightly above 1000 C. so that the uppertemperature limit for using the known nickel base superalloys may onlyjust exceed 900 C.

The novel alloys are very well suited for hard facing machine partssubjected to high temperatures. Due to the high strength characteristicsat high temperatures and its ductility, the molybdenum containing alloycan be directly used for the manufacture of turbine blades and vanes.

We claim:

1. A cobalt base alloy consisting essentially of, 5 to 10 percent ofnickel, by weight, from about 15 to about 30 percent of chromium, 10 to20 percent of tungsten, 5 to 10 percent of nickel, and about 0.5 to 3percent of zirconium boride ZrB the balance being cobalt.

2. The alloys as claimed in claim 1 wherein nickel is replaced partiallyby molybdenum.

References Cited UNITED STATES PATENTS 2,126,742 8/1938 Golyer 2,126,7438/1938 Golyer 75 171 2,126,745 8/1938 Golyer 75-171 2,126,749 8/1938Golyer 75-170 2,309,371 1/1943 Wissler 75-171 2,704,250 3/1955 Payson75-171 DAVID L. RECK, Primary Examiner. HYLAND BIZOT, RICHARD O. DEAN,Examiners.

1. A COBALT BASE ALLOY CONSISTING ESSENTIALLY OF, 5 TO 10 PERCENT OFNICKEL, BY WEIGHT, FROM ABOUT 15 TO ABOUT 30 PERCENT OF CHROMIUM, 10 TO20 PERCENT OF TUNGSTEN, 5 TO 10 PERCENT OF NICKEL, AND ABOUT 0.5 TO 3PERCENT OF ZIRCONIUM BORIDE ZRB2, THE BALANCE BEING COBALT.